Add composite index to articles hotness_score and comments_count (#13724)

db/migrate/20210511073505_add_index_on_articles_hotness_score_comments_count.rb

@@ -0,0 +1,15 @@
+class AddIndexOnArticlesHotnessScoreCommentsCount < ActiveRecord::Migration[6.1]
+  disable_ddl_transaction!
+
+  def up
+    columns = %i[hotness_score comments_count]
+
+    add_index :articles, columns, algorithm: :concurrently unless index_exists?(:articles, columns)
+  end
+
+  def down
+    columns = %i[hotness_score comments_count]
+
+    remove_index :articles, column: columns, algorithm: :concurrently if index_exists?(:articles, columns)
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2021_04_30_094954) do
+ActiveRecord::Schema.define(version: 2021_05_11_073505) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "citext"
@@ -161,6 +161,7 @@ ActiveRecord::Schema.define(version: 2021_04_30_094954) do
     t.index ["comments_count"], name: "index_articles_on_comments_count"
     t.index ["featured_number"], name: "index_articles_on_featured_number"
     t.index ["feed_source_url"], name: "index_articles_on_feed_source_url", unique: true
+    t.index ["hotness_score", "comments_count"], name: "index_articles_on_hotness_score_and_comments_count"
     t.index ["hotness_score"], name: "index_articles_on_hotness_score"
     t.index ["path"], name: "index_articles_on_path"
     t.index ["public_reactions_count"], name: "index_articles_on_public_reactions_count", order: :desc